1. Field of the Invention
The present invention is related to transmitting commands from a central processor to a peripheral unit and, more particularly, to transmitting commands excluded from predefined commands for the peripheral unit known to the operating system controlling operation of the central processor.
2. Description of the Related Art
As illustrated in FIG. 1, a typical computer system of any size includes a central processor 10 which executes, in broad terms, two types of software. The type of software which computer users are most familiar with is generally termed application software 12. Examples of application software are word processors, accounting programs, database managers, communication programs, etc. Execution of application software requires an operating system 14. There any many modules included within an operating system. One module, driver software 16, is of primary interest although there are other operating system modules 18 which are also included in the operating system 14.
Most computer systems also include peripheral equipment 20 which is connected to the processor 10 by interface electronics 22. The number of components included in the interface electronics varies depending upon the complexity of the computer system. Examples of peripheral equipment 20 are disk drives, tape drives, modems, etc. The driver software 16 in the operating system 14 is required for most application software 12 to communicate with peripheral equipment 20.
Most computer systems are manufactured by companies which permit other companies to produce peripheral equipment for use with their computer systems. In some cases, the peripheral unit manufacturer provides the driver software 16, while in other cases, all modules of the operating system 14 are provided by the same vendor, typically the manufacturer of the computer system which includes the processor 10. In the latter case, the peripheral equipment manufacturer is limited to using the commands which can be communicated through the operating system 14. Even in the former case, the other operating system modules 18 between the application software 12 and driver software 16 may limit the types of commands which can be transmitted by the application software 12 to the driver software 16. As a result, the functions performed by the peripheral equipment 20 can be limited by a lack of foresight on the part of the designer of the operating system 14.